The difference in installation height directly affects the oil absorption efficiency. When the fuel pump is higher than the liquid level in the fuel tank (such as when installed on a pickup truck chassis), an additional static pressure resistance of 0.0098MPa needs to be overcome for every additional 10 centimeters of vertical distance. The measured data of the Ford F-150 shows that when the fuel tank level of the oil pump installed in the engine compartment is lower than 1/4, the vacuum degree of the oil inlet pipeline needs to reach -65 kpa to maintain normal fuel supply, and the energy consumption is 22% higher than that of the built-in fuel tank scheme. For modified vehicles with a liquid level drop of more than 80 centimeters, the probability of fuel cavitation increases to 4.3 times the normal value.
The dynamic posture of the vehicle changes the hydraulic characteristics of the oil circuit. When the sports car accelerates sharply (with an acceleration > 0.8G), the liquid level at the front end of the rear fuel tank drops by up to 12 centimeters, resulting in a sharp increase in the risk of the front fuel pump’s suction port being exposed. The solution for the Porsche 911 GT3 is to integrate a 30cm³ oil storage tank at the bottom of the pump body, which can maintain continuous fuel supply for 8 seconds under full throttle. Comparative tests show that this design reduced the fuel pressure fluctuation from ±25% to ±7% at the S-turn of the Nurburgring Circuit.
The difference in heat dissipation environment leads to the deviation of lifespan. The working environment temperature of the fuel pump installed in the engine compartment is 42℃ higher than that in the fuel tank (the measured peak temperature in summer is 89℃ vs 47℃). Chrysler’s maintenance statistics confirm that the average lifespan of this type of pump body is only 65,000 kilometers, which is 55% shorter than that of the submersible scheme. High temperatures also increase the resistance of the motor windings by 18%, resulting in a 14% rise in power consumption and accelerating the wear rate of the carbon brushes of the electronic commutator to 2.3μm per thousand kilometers.
Vibration load is related to mechanical reliability. The vibration intensity in the truck chassis area of the non-load-bearing body reaches 12.3Grms, which is three times that of the fuel tank area. For the Isuzu D-MAX with an external Fuel Pump on the chassis, the clearance of the pump body bearing expands to 0.15mm after traveling 80,000 kilometers (0.07mm for the built-in pump in the fuel tank), resulting in a 17% flow attenuation. The response strategy of Mitsubishi L200 is to install a hydraulic shock-absorbing base, which reduces the vibration transmission rate by 68%.
The collision safety layout needs to follow the ISO 8855 standard. Studies show that vehicles with oil pumps installed behind the rear axle have an 83% higher probability of pipeline rupture when rear-end collisions occur at 50km/h than those with side-mounted fuel tanks. The Volvo XC90 places the pump body in the protected area below the B-pillar and is equipped with a rigid bracket (with a compressive strength of ≥500MPa), achieving a 100% integrity rate of the fuel supply system in the IIHS crash test. However, this design will increase the length of the oil pipe by 2.4 meters, raising the pressure loss of the pipeline by 0.02MPa.
Location optimization can bring economic benefits. The Renault Clio fuel tank integrated oil pump solution reduces assembly time by 40 minutes per unit, shortens the wiring harness length by 3.2 meters per vehicle, and saves 37% in material cost per unit. Data from Chevrolet dealers confirm that the optimized layout has reduced the failure rate from 12.7 cases per thousand vehicles to 4.3 cases, and the maintenance cost during the warranty period has decreased by 58,000 yuan per million kilometers. However, the event modification requires trade-offs: Moving the oil pump to the firewall can reduce the weight by 1.2kg, but it will increase the cost of the explosion-proof shield by $210.